CH 221--Ziegler
Chapter 8,9
KEY CONCEPTS
Class period 1 -- Reading pp. 275- 278(t)
1. State the number of valence electrons for a main-group element. Problem 8.1
2. Draw the electron-dot symbol for a main-group element. Problems 8.5, 8.6
3. State the “octet rule.” Problem 8.2
Class period 2 -- Reading pp. 280 – 291
4. Identify periodic trends in electronegativity. Problems 8.33
5. Predict the polarity of a bond. Problem 8.35, 8.36
6. Draw Lewis structures for molecules and polyatomic ions. Problems 8.43, 8.44.
Class period 3 -- Reading pp. 292- 297, 315 – 323; 328 -329 (b)
7. Use calculated Formal Charges to evaluate Lewis structures. Problem 8.46
8. Write resonance forms. Problems 8.47, 8.48 a and b
9. Use the Lewis structure to predict molecular geometry and bond angles. (Note:
you will be required to do this only for molecules and ions in which the octet rule
is satisfied for all atoms.) Problems 9.11 a-d., 9.15, 9.16
10. From the geometry of a polyatomic ion or molecule, predict whether it is polar
or nonpolar. Problems 9.22, 9.25, 9.27.
Class period 4 -- Reading pp. 330 – 334(b), 336 – 339
11. State the hybridization in a covalently bonded species. Problem 9.43
12. State the number of pi and sigma bonds in a molecule or polyatomic ion.
Problems: For the molecules in Problems 9.43, 9.16 and 9.27, state the number
of sigma and pi bonds in each molecule
Answers to Problems:
8.1 See Text A-8
8.2 The octet rule is the observation that atoms will gain lose or share electrons to achieve the
stable configuration of 8 valence electrons. The reason it is in quote marks is that it has so
many exceptions. Specifically, H, He, and pretty much everything in the lower periods.
8.5 See Text A-8.
8.6 a)
M
gii
b)
A
s
•
••
ii
c)
[]
3
3::
Sc or Sc
+
+
⎡
⎤
⎢
⎥
⎣
⎦
ii
ii
d)
2
::Se
−
⎡
⎤
⎢
⎥
⎣
⎦
ii
ii
8.33 See Text A-9
8.35 See Text A-9
8.36 NOTE: The answer book refers you
to Figure 8.9 when they mean Fig 8.6
a) O-F < C-F < Be-F
